Gas producer



Nov. 23, 1 37- e. SZIKLA ET AL- GAS PRODUCER Filed April 11, 1954 Wig]Patented Nov. 23, 1937 UNITED STATES ao'sassa GAS PRODUCER Gza 'Sziklaand Arthur Rodrick, Budapest, man

Application April 11, 1934, Serial No. 720,138

, In Germany April 18, 1933 10 Claims. (Cl. 48- 16) This inventionrelates to a process and apparatus for complete or partial gasifying ofcombustible dust, espec'iallycoaLdust consisting of particles ofdifferent sizes for example up to 5 mm.,

5 according to which the distilling and gasifying of the coal dustintroduced into the gasifylng cham ber takes place in a rising gascurrent preferably in the manner set forth for example in our U. 8.

Patent 1,869,949, issued August 2, 1932, in continuous circulationthrough the gasifying chamber and an adjacent dust collecting chamber,from which latter the incandescent coke dust is re-introduced into therising gas current of the gaslfying chamber. It will be understood thatin order to secure an intensive gasifying of the coked coal dust and tosecure the-separation of the slag from the dust, it is necessary tomaintain a high temperature in the space in which the gasification takesplace. This temperature would be, however, detrimental for the walls ofthe upper parts of the gasifying chamber as well as of the dustcollecting chamber and would produce besides the sintering or caking ofthe slags.

The object of this invention is to eliminate the drawbacks abovereferred to in spite of the use of high gasifying temperatures.According to this invention the generator gases produced at a hightemperature are cooled to a nondetrimental temperature by means of freshcoal dust, introduced or projected into the upper part of the gasifyingchamber, preferably at a pointopposite the passage of the generatorgases into the dust collecting chamber, said fresh coal dust being cokedat the same time. The gas pro- 5 ducer is therefore provided at theupper part of the gasifying chamber with a substantially horizontallyacting projecting device for the introduction of fresh coal dust adaptedto produce in the inlet passage of the dust collecting chamber, at 4.0 acertain distance from the top of the gasifylng chamber, a coal dustscreen.

Thereby a sufliciently high temperature may be maintained in thegasifying chamber, especially in its lower part, to secure an intensivegas!- 45 fying of the coked incandescent coal particles and to secure asuiiicient fluidity of the slags to allow the particles of molten slagsto unite to form comparatively large drops. In consequence the majorpart of the slag will drop directly within 50 the gasifying chamber andthrough the bottom opening thereof into the slag collecting space, sothat only a comparatively small part of the slag will be transferredinto the dust collecting cham ber. The screen of fresh coal protects thetop 5501 the gasifying chamber against the radiating heat of thecombustion zone as well as against blast flames and cools the generatorgases produced in the gasifying chamber before their reaching the dustcollecting chamber, so far that the liberated slag particles and thoseof the coke 5 dust remain in a loose state and do not sinter or fuse toform a cake.

The annexed drawing shows as an example a coal dust gas produceraccording to the invention.

With reference to the drawing, I is the gaslfying chamber, 2 its bottomand 3 an opening therein for the introduction of -the gasifying air. 4is a horizontally adjustable slide to regulate the cross sectldnal areaof bottom opening 3, H is the l5 opening for introduction of the.fresh.coal dust provided with the projecting device l2. This latter isadapted to project the dust fed through funnel IS in a substantiallyhorizontal. direction across the gasifying chamber, so that the fresh 0"coalforms a screen l4 extending across the horizontal cross sectionalarea of the gaslfying chamber into the dust collecting chamber 5. Thislatter communicates with the gasifying chamber l in the proximity of itstop by means of an open- 25 ing 1, located preferably opposite theopening I I.

In order to provide eflicient cooling of the rising gases and eliectiveprotection of the top of the gasifying chamber against hightemperatures, as well as to prevent the formation of slag accu- 30mulatlons at the top by upwardly projected slag particles, theprojecting device I! or the orifice II is located in such a manner inthe upper part of the gaslfylng chamber, that the screen I formed by theprojected, coal particles, partly or completely occupies the upper space22. The gas generated with a high temperature rises in shaft I andenters space 22 while penetrating the coal screen I. Thereby a heatexchange takes place under very favorable conditions, caus- 40 mg thecooling of the gas and the solidifying of the slag particles. It will beunderstood that this cooling of the gases by the introduction of fresh,cool coal is not detrimental to the overall thermal efficiency of thegas producer. It will be understood that the thermic and pyrometriceifect or eff ciency of the total combustion is not affected at all, butthe cooling effect of the fresh coal lowers the temperature of thegenerated gases, while the heat withdrawn from the gases is utilized forthe coking of the freshcoal. The intermediary cooling of the producergases by the introduction of fresh coal has no effect on the ultimatetemperature attained in the upper reglon of combustion chamber 19, bythe subsefeeding dry coke dust into the producer, the composition andtemperature of the combustible gas p oduced would be the same with orwithout intermediary cooling. In using a coal rich in gases, thecomposition of the gas produced with intermediary coolingwill bedifferent from that obtained without cooling and will be more desirable,as the fresh coal isdistilled in the absence of oxygen, that is to say,outside of the combus-.

tion zone of the gasifying shaft.

The intermediary cooling has therefore no drawback whatever, but has thegreat advantage of allowing high temperatures in the gasifying chamber,which secure the separation of the slags in liquid state.

According to this process incandescent coke will be gasified in thegasifying chamber at high temperatures and the high temperature of thegases produced will be decreased usefullyby utilizing the heat of saidgases for the drying, distilling, coking and heating of the fresh coalto the temperature of incandescence.

If a rotating wheel is used for the introduction of the coal dust, theshape, or more or less horizontal position of the coal dust screen ll,may be synchronized with the operating requirements of the gas producer,either by changing the point of impact of the coal dust on the wheel, orby changing the speed of said wheel.

The dust collecting chamber and the gasifying chamber communicate in theproximity of their respective bottoms by means ofa channel 8, throughwhich the coke dust is returned from the dust collecting, chamber intothe gasifying chamber. An inclined choke surface 9 is provided at thegasifying-chamber end of channel 8 and opposite thereto, at the dustcollecting chamber end of channel 8, a reciprocating plunger l0, or aplurality thereof, are provided to push the coke dust collected inchamber 5 into channel 8. Owing to the resistance of the choke surface9, the pushing of the coal dust is counteracted by a substantialpressure, so that the coke dust will be strongly compressed in channel8. This will prevent the gas in the proximity of the bottom of thegasifying chamber,- the pressure of which exceeds the gas pressure inthe dust collecting chamber, from blowing back'the coke dust and thisarrangement also prevents the streaming of air from the gasifyingchamber immediately into the dust collecting chamber through channel 8.

The water cooled scraper i6 above the plungers l0 removes the coke dustfrom the upper face of the plungers.

It is essential that the slide I controlling the width of the bottomopening 3 may be located at the side of the bottom opening adjacent tothe return channel 8, because here the coke dust accumulation isconstantly maintained by the stufling action of the plun ers l0 and iskept in motion towards the wor ng edge of slide l,

whereby any accumulation of slag in the gap between slide 4 and bottomplate 2 is prevented.

The operation is as follows:

The coal dust projected through aperture li into the gasifying chamberenters the rising hot gas stream and will be coked. As the producergases coming into contact with the coal dust do not contain oxygen, thegases of distillation do not undergo any combustion, but enrich theproducer gases with hydrocarbons which when burnt in chamber ill willproduce a radiating flame. The dropping incandescent coke dust will begasified in the shaft I. By suitably adapting the air admission to thequantity of coal fed, a temperature can be obtained at which the slagmelts and drops from the circulation through bottom opening 3. The top 6of the gasifying chamber is protected against the high temperature ofthis latter by the direct screening eifect of coal dust screen it. Butthe fresh coal dust has be sides a cooling effect on the rising producergas by heating the coal and evaporating of its moisture. The,distillation of the fresh coal and the decomposition of steam, if suchbe present consume heat, while no new heat is generated, be.- cause inthis part of the, chamber no more free oxygen is present, so that nocombustion can take place. The introduced fresh coal dust, after havingbeen subjected to a distillation and being in incandescent state, eitherenters the dust collecting chamber 5 or drops through quiescent zones inthe proximity of the walls of the gasifying chamber towards its bottom.The gases cooled in the above describedlmanner enter the dust collectingchamber 5 with a temperature substantially lower than thetemperature ofthe "producer gases, and at. which the slag granulates.

The incandescent coke dust accumulating in the dust collecting chamberis loose and rolls from the dust bank'l8 towards the return channel 8.The coking of incompletely coked coal particles is completed on the dustbank IS. The producer gases, substantially freed from suspended cokedust, are conducted to their final destination, where they are burnt,for example, under a boiler in combustion chamber i9 with secondary airadmitted through channels 20.

The temperature stages of the gas can easily be calculated on the basisof an analysis-of the coal supposing a heat exchange. The temperature ofthe gas produced in the'gasifying shaft from incandescent coal iscalculated to be about 1480" C. for all kinds of coal, if completeconversion to carbon dioxide be assumed.

By using brown coal with lower heating value of 5300 cal., 38% cokecontent, 14% moisture and 8.5% ash, for example, the temperatureresulting from the introduction of fresh coal dust can be calculated to970 C. without considering the decomposition of water vapours.

The temperature difference reached practically is smaller, owing to theincomplete exchange of heat. In a continuously working plant thetemperature measured in the gasifying shaft was' perature is suillcientto realize practically the advantages of the process according to theinvention. The rate of heat *exchange and the temperature decreasereached thereby can be controlled by the degree of fineness of the coaldust,

by the dimensions of the gasifying shaft and of the dustcollecting'chamber as well as by the construction of the projectingdevice for the fresh c'oal dust.

The heat exchange between the gas'and the coal may often be sufllcientand the cooling ofthe gas can be increased by the following means:

a. Increase of the time of dropping of the coal particles by retardingtheir fall by means of baflle plates inserted in the path of travel ofthe gases adapted to accumulate the dropping coal particles and allowthem to trickle again into the gas current. In the drawing, for example,three alternating baiiles 25, 26 and 21, form a cascade the coalparticles and the gases. The lowest baflle 21 is arranged in such amanner as to direct the falling dust in front of the stuffing plungers'I0 while the gas current is diverted and accelerated in such a manner asto promote the separation of dust and gas.

b. By water cooling. This may be eifected either by moistening the freshcoal or by introducing finely dispersed water at suitable places, forinstance, at the entrance to the dust'collecting chamber through opening28 directly into the gases.

0. By cooling'by means of a cooling the example shown in the drawing thetop of the gasifying chamber is formed by tubes 29. This construction isadvantageous for the reason that rid. In

it allows the top to be inclined in a favourable considerable, while ifthe gas is strongly cooled by the coal, it will give off less heattowards the,

grid.

d. The heat exchange may be further increased and the temperature of thegasifying chamber enhanced by inclining the upper end 24 of thepartition 23 between the gasifying chamber and the dust collectingchamber towards the former so as to narrow upwards the upper end of theshaft 1. Thereby" the loss of heat of the gasifying shaft by radiationtowards the coal dust screen i4 and the grid 29, if any, is restricted,so that the temperature insaid shaft will rise.

In certain cases it may be desirable to lower the range of temperaturesof the whole process. For this purpose suitable quantities of burntgases, and/or steam are mixed with the primary air introduced throughthe bottom aperture 3. The carbon dioxide of the combustion gases or thesteam will be decomposed under heat absorption in the shaft by theincandescent coke, whereby the temperature'of the producer gas islowered.

even before it reaches the coal dust screen. The admission of steamproduces gases of lower temperature, since part of the coke is gasifledby the steam to produce a correspondingly smaller volume of gases thanwould be obtained by using air, of which four-fifths is inert nitrogen.This smaller volume of gases will be cooled to a greater degree by theintroduction of a given quantity of fresh coal.

The process of gasifying takes place in the conditions of equilibrium,if the quantity of introduced primary air is suflicient to gasify thetotal quantity of introduced coal. Suppose that the efiieiency ofcooling and the proportion of air and coal are the same, the cooling ofthe producer gas by the coal (and not by the additional cooling of waterinjection or cooling grid and the like) will be the same at differentloads, because the same unity of fresh coal corresponds to the unity ofgas, independently from the load.

Hence the temperature of the cooled gas current is the means to controlthe process, by influencing the quantity of primary air admitted independence upon said temperature. Accordingly, if the temperature of thegas current in chamber 5 is too high, the admission of primary air isrestricted, whereby the quantity of gas produced is decreased and iscooled to a greater degree by the fresh coal. On the other hand, byincreasing the quantity of primary air, more gas of high temperature isproduced if the temperature of the gas current in 5 is too low. Thisgreater volume of gas will be cooled to a lesser degree by the samequantity of fresh coal. This regulation can be effected automatically bymeans of a temperature measuring instrument (not shown) influenced bythe temperature of the gas current in chamber 5.

What we claim is:

1. In a gas producer for gasifying and distilling combustible dust,especially coal dust, a gasifying chamber with a bottom opening foradmission of air and removal of slags, a regulating means controllingsaid opening. a dust collecting chamber communicating with the gasifyingchamber at its upper part and receiving hot gases and coke dust fromsaid gasifying chamber, a coke dust return channel directly connectingthe .bottom portions of said chambers and ending at the bottom of thegasifying chamber whereby continuous circulation of coke dust throughsaid gasifying chamber and said dust collecting chamber is permitted,and a device provided at the upper part of the gasifying chamber forintroducing fresh coal dust in the shape of a screen across the crosssectional area of at least one of said chambers whereby the producergases generated in said gasifying chamber are cooled to a temperaturelower than. the melting temperature of the slag.

2. A gas producer according to claim 1, in which the device forintroducing the fresh coal dust is arranged in such a' manner that thecoal dust screen divides the gasifying chamber into two superposedparts, the upper of which is at least partly occupied by the coal dustscreen.

3. A gas producer according to claim 1, in which the device forintroducing the coal dust is located opposite to the opening leadinginto the dust collecting chamber.

4. A gas producer according to claim 1, in which a choke surface isprovided at the gasifying chamber end of the dust return channel,reciprocating plungers being arranged in the dust collecting chamberopposite to said choke surface adapted to stuif the coke dustaccumulated at the bottom of the dust return channel into said channel.

5. A gas producer according to claim .1, in which the regulating meanscontrolling the width of the bottom opening of the gasifying chamber islocated at the return channel side of said bottom opening. V I

-6. A gas producer according to claim 1, in

which baiile plates receiving the dropping coal.

particles are provided in the dust collecting chamber to interrupt thefall of said particles and to form a multiple cascade of coal dust.

7. A gas producer according to claim 1, in which a. water injectingtube. is arranged in the upper part ofat least one of saidchambers.

8. A gas producer according to claim 1, in which cooling tubes arearranged at the top of the gasifying chamber.

9. A gas producer according to claim 1, in which a partition is providedbetween the gasitying and dust collecting chambers, said partition beinginclined at its upper part so as to narrow upwardly the cross sectionalarea of the gasifying chamber.. a

10. In a gas producer of the character deing for admission of air andremoval oislags, a dust collecting chamber, said chambers communieatingwith one another at the top and bottom,

the communication at the bottom being above said air admission openingand normally being closed by collected dust, mechanical means foradvancing dust from said dust collecting chamber to said gasifyingchamber through said communication, and means for introducing fresh coaldust into the upper part 01 said gasifying chamber in the shape of ascreen which extends across the cross-sectional area 01 the gasifyingchamber, whereby the producer gases generated in said gasifying chamberare cooled to a temperature non-detrimental to the walls of the upperpart of said gaslfying chamber. v

GEZA SZIKLA.

ARTHUR ROZINEK.

